Prayer is close to the heart of many religious traditions. Prayer represents the human side of the hypothesized two-way communication between people and their God or gods. What people think they are doing when they are praying and what effect prayer has on the people who are doing the praying or on the people for whom prayer is offered are questions which have occupied psychologists and other empirical scientists of religion for well over a century.

The gauntlet was first thrown down for a proper scientific investigation of prayer by the 19th-century statistician Sir Francis Galton in two influential publications in 1872 and 1883. Galton argued that questions about the nature and effectiveness of prayer were not merely matters for philosophical and theological speculation, but were properly matters for empirical enquiry. The key research since Galton's pioneering challenge can best be summarized within three research categories concerned with the understanding of prayer, with the subjective effects of prayer, and with the objective effects of prayer.

Key research into the development of an understanding of prayer during childhood and adolescence was pioneered during the 1960s by Robert Thouless and Laurence Brown. In one of his studies, grounded in developmental psychology, Brown explored the responses of 398 boys and 703 girls between the ages of 12 and 17 to seven situations: success in a football match, safety during battle, avoidance of detection of theft, repayment of a debt, fine weather for a church fete, escape from a shark, and recovery of a sick grandmother. In relation to each situation he addressed two questions: Is it right to pray in this situation? Are the prayers likely to have any effect? The data demonstrated a consistent age-related trend away from belief in the causal efficacy of petitionery prayer. A second classic study grounded in developmental psychology and concerned with age-related stages in religious thinking during childhood and adolescence was reported by Ronald Goldman in the 1960s. Goldman employed projective picture tests to uncover the thinking of 200 young people between the ages of 8 and 16. He concluded that young people's concepts of prayer changed according to a fixed stage developmental sequence in accordance with Jean Piaget's model of intellectual development from preoperational thinking, through concrete operational thinking, to abstract operational thinking.

A very different theoretical framework was taken by Brown in two studies published in the 1990s grounded in social psychology. This time Brown examined the influence of home, church, and denominational identity on an attitudinal predisposition to pray and the practice of prayer among 4,948 11-year-olds and 711 16-yearolds. He demonstrated that among 16-year-olds the influence of church was stronger and the influence of parents weaker than among 11-year-olds. From these data he concluded that children and adolescents who pray were more likely to do so as a consequence of explicit teaching or implicit example from their family and church community than as a spontaneous consequence of developmental dynamics or needs.

The first study concerned with assessing the subjective effects of prayer on those who were doing the praying was reported by Francis Galton in his 1872 paper. Galton argued that clergy were a more prayerful group of people than either doctors or lawyers, and that if their prayers were effective, clergy should be expected to live longer than the other two groups. His first set of data, based on 945 clergy, 294 lawyers, and 244 medical men indeed demonstrated a higher life expectancy among clergy, but Galton dismissed this finding as evidence of the effectiveness of prayer on the grounds that their greater longevity might more readily be accounted for by their "easy country life and family repose." In recent years a great deal of serious research has been invested in monitoring the subjective effects of prayer on those who were doing the praying. Such studies have been conducted among the general population and among groups that merit special attention, especially among the sick and among the elderly. The general consensus is that prayer is associated with a wide range of positive psychological benefits. Building on this tradition of research, Leslie J. Francis published four papers in the 1990s and 2000s examining the relationship between prayer and purpose in life among different samples of young people between the ages of 12 and 15. He found that increased levels of prayer were associated with higher levels of purpose in life, irrespective of whether the young people attended church. One of the studies was based on young people who never attended church; those who prayed in this sample recorded a higher sense of purpose in life. Another study was based on young people who attended church weekly; those who prayed in this sample recorded a higher sense of purpose in life. Francis advances the following theory to account for these findings. He argues that young people who pray are, consciously or unconsciously, acknowledging and relating to transcendence beyond themselves. Acknowledging such transcendence and relating to that transcendence through prayer places the whole of life into a wider context of meaning and purpose. The following psychological mechanism proposes a causal model according to which prayer may influence purpose in life. The practice of prayer implies both a cognitive and an affective component. The cognitive component assumes, at least, the possibility of a transcendent power. Such a belief system is likely to support a purposive view of the nature of the universe. The affective component assumes, at least, the possibility of that transcendent power being aware of and taking an interest in the individual engaged in prayer. Such an affective system is likely to support a sense of value for the individual.

The first study concerned with assessing the objective effects of prayer on those for whom others were praying was also reported by Francis Galton. This time Galton argued that members of royal families were the most prayed for group of people and that if prayers for royal families were effective, royalty should be expected to live longer than comparable groups. His set of data, based on 97 members of royal houses, 1,632 gentry, 1,179 English aristocracy, 945 clergy, 569 officers of the army, and several other groups demonstrated that far from being the longest lived, the royalty were the shortest lived of all the groups he studied. He concluded that prayer has no efficacy. In recent years a great deal of serious research has been invested in monitoring the objective effects of prayer on those for whom others were praying. The best known of these studies, by Randolph C. Byrd, was published in the Southern Medical Journal in 1988. Byrd's study was concerned with the therapeutic effects of intercessory prayer in a coronary care unit. Over a 10-month period, 393 patients admitted to the unit were randomized, after signing informed consent, to an intercessory prayer group or to a control group. The patients, staff, doctors, and Byrd himself were all unaware which patients had been targeted for prayer. The prayer treatment was supplied by "born again" Christians. The intercessory prayer was done outside the hospital daily until the patient was discharged from the hospital. Under the direction of the coordinator, each intercessor was asked to pray daily for rapid recovery and for prevention of complications and death. Although there were no differences between the prayer group and the control group at the time of entry to the unit, a significantly better rate of recovery was experienced by the prayer group. In 1999, in the Archives of Internal Medicine, William S. Harris published a replication and extension of Byrd's pioneering study. This study involved 1,013 patients randomized at the time of admission to receive remote intercessory prayer (prayer group) or not (usual care group). The data demonstrated that compared with the usual care group, the prayer group experienced a significantly better outcome.

The important point is that both of these studies were conducted to the scientific standards employed in medical research to assess the effectiveness of different medical procedures, treatments, and drugs. It is odd that such studies are not better known by and taken more seriously by those properly concerned with the value of religious and spiritual development. In conclusion, the empirical evidence demonstrates that prayer makes a positive contribution to the youth and human development of those who pray and may also carry beneficial consequences among those for whom prayer is offered.